[Intel-gfx] Skylake graphics regression: projector failure with 4.8-rc3

[Zanoni, Paulo R]

Hi

Em Qua, 2016-08-31 às 14:43 -0700, James Bottomley escreveu:
> On Wed, 2016-08-31 at 11:23 -0700, James Bottomley wrote:
> > 
> > On Fri, 2016-08-26 at 09:10 -0400, James Bottomley wrote:
> > > 
> > > We seem to have an xrandr regression with skylake now.  What's
> > > happening is that I can get output on to a projector, but the 
> > > system is losing video when I change the xrandr sessions (like 
> > > going from a --above b to a --same-as b).  The main screen goes 
> > > blank, which is basically a reboot situation.  Unfortunately, I 
> > > can't seem to get the logs out of systemd to see if there was a 
> > > dump to dmesg (the system was definitely responding).
> > > 
> > > I fell back to 4.6.2 which worked perfectly, so this is
> > > definitely 
> > > some sort of regression.  I'll be able to debug more fully when
> > > I 
> > > get back home from the Linux Security Summit.
> > 
> > I'm home now.  Unfortunately, my monitor isn't as problematic as
> > the
> > projector, but by flipping between various modes and separating and
> > overlaying the panels with --above and --same-as (xrandr), I can
> > eventually get it to the point where the main LCD panel goes black 
> > and can only be restarted by specifying a different mode.
> > 
> > This seems to be associated with these lines in the X
> > 
> > [ 14714.389] (EE) intel(0): failed to set mode: Invalid argument
> > [22]
> > 
> > But the curious thing is that even if this fails with the error 
> > message once, it may succeed a second time, so it looks to be a 
> > transient error translation problem from the kernel driver.
> > 
> > I've attached the full log below.
> > 
> > This is only with a VGA output.  I currently don't have a HDMI 
> > dongle, but I'm in the process of acquiring one.
> 
> After more playing around, I'm getting thousands of these in the
> kernel
> log (possibly millions: the log wraps very fast):
> 
> [23504.873606] [drm:intel_dp_start_link_train [i915]] *ERROR* failed
> to train DP, aborting
> 
> And then finally it gives up with 
> 
> [25023.770951] [drm:intel_cpu_fifo_underrun_irq_handler [i915]]
> *ERROR* CPU pipe B FIFO underrun
> [25561.926075] [drm:intel_cpu_fifo_underrun_irq_handler [i915]]
> *ERROR* CPU pipe A FIFO underrun
> 
> And the crtc for the VGA output becomes non-responsive to any
> configuration command.  This requires a reboot and sometimes a UEFI
> variable reset before it comes back.

Please see this discussion:
https://patchwork.freedesktop.org/patch/103237/

Do you have this patch on your tree? Does the problem go away if you
revert it?

Thanks,
Paulo

> 
> James
> 
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